We have Geothermal heating using 2 bore holes (each 370ft+) with 1/2 mile of pipe in them plus about a ¼ mile horizontally in the ground. The government pay us about £6,600 a year to run the system over a period of 7 years, there just under 6 years left to run. The system put in is incredibly efficient and has a very high heat output for it’s size.
Solar energy PV
We have 4Kw solar PV for which the government pay us approximately £700 pa and will do so for another 17 years. This is an unusual system in that we do not export any electric into the grid. The government estimates domestic systems export 50% of what they generate and pay the household extra for this but I have (legally) an electronic controller that diverts all export electric into immersion heaters. This means for about 8 months of the year we have masses of free hot water, more than we can use.
We have a further a 1.5Kw solar PV which has no grant but the power heats the water in the heating system.
Solar hot water/storage for geothermal
On the roof, again with no grant, there are 150 solar hot water vacuum tubes. The heat from these is put into the house central heating system. This system is massive for a domestic property and would normally be enough to power 2 or 3 average houses. Even a sunny day in mid winter the system produces warm water but in the summer the system peaks, on a sunny day, producing in the region of 16Kw. This is massive especially as the house does not need heat in the summer. In fact it is so well insulated it needs cooling. It sound crazy but this very large excess of hot water is automatically reverse fed, through the geothermal system, heating the field. The thousands of tons of soil near the pipes in the field act as heat storage and by heating this ground, even a small amount, the heat can be pulled back into the house heating system in the winter making the geothermal boiler even more efficient.
The house sees the sun from sunrise to sunset and gets a very large solar gain especially from the 2 conservatories. To capitalise on this passive solar gain I have put in 2 automatic air pump systems which pump the hot air from the top of the conservatories into the house. It adds a significant amount of heat into the house. Because there is so much solar input and the house is so well insulated it needs the central heating for probably less than 3 months of the year.
Rather than extractors in each bathroom and kitchen, as is required by current building regulations, I have installed a whole house ventilation system. This recovers waste heat from the extracted air from the kitchen and bathrooms and puts the heat back into the house. This is a special system in that you can turn off the heat exchangers so no heat is put back into the house in the summer instead it is converted into an air-conditioning system. 2m down in the ground and connected to the ventilation system are 2 x 10 inch silver lined (the silver lining has anti-bacterial properties) pipes each 30m long. Being deep in the ground these pipes, which duct the input air to the system, warm the very cold air in the middle of winter to about 10C so the air enters the warmer than the outside. In the summer, with the exchangers off, this 10C air is used to cool the whole house. This systemonly costs about £2/week to run.